To reduce wind flow resistance and drag on a trailer, truck, semi-trailer, or other vehicle, side skirts that extend downwardly from a bottom of the trailer and/or chassis toward the roadway to partially enclose the floor assembly and undercarriage have been utilized.
Air flow passing under a ground vehicle imparts a drag force to the vehicle when it impinges on and flows around the vehicle undercarriage components attached to or a part of the underside of a vehicle. Side skirt systems are designed to prevent or control the flow of air from entering the undercarriage region from a side of the ground vehicle, such as a trailer of a tractor-trailer truck system, for example. Such reduction on the drag of the ground vehicle may operate to conserve fossil fuels as well as other sources of vehicle drive power for hybrid vehicles, battery-operated vehicles, and/or alternative fuel-based vehicles, for example.
Truck trailers typically have a higher elevation than passenger vehicles. This presents a risk that a passenger vehicle may underride the trailer in an accident, potentially resulting in damage to the underriding vehicle and injury to occupants therein. Accordingly, a side protection device, or underride guard, may be provided for use with a trailer in order to reduce the risk of such passenger vehicles underriding the trailer. Side protection devices are intended to reduce the extent to which a “passenger vehicle” (as defined in 49 C.F.R. Part 571 §) can intrude under the side of a trailer, diminishing passenger compartment intrusion.